Liquid separation membrane for pervaporation

Abstract

A liquid separation membrane for pervaporation composed of a polymeric substance having in the main chain a glycosidic skeleton containing cationic groups and/or anionic groups at least some of which form a salt with counter anions and/or counter cations; and a method for pervaporation, which comprises separating a water-organic liquid mixture or an organic liquid-organic liquid mixture by pervaporation using a separation membrane, said membrane being composed of a polymeric substance having in the main chain a glycosidic skeleton containing cationic groups and/or anionic groups at least some of which form a salt with counter anions and/or counter cations and being dried so as to have a water content of not more than 25% by weight.

What is claimed is: 
     
       1. A membrane for pervaporation composed of a salt of chitosan containing at least 2 mole % of nonpolymeric polybasic acid ion based on the amino groups of the chitosan. 
     
     
       2. The membrane for pervaporation of claim 1 in which the polybasic acid is sulfuric acid. 
     
     
       3. The membrane for pervaporation of claim 1 in which the polybasic acid is phosphoric acid. 
     
     
       4. A membrane for pervaporation composed of a salt of chitosan containing at least 2 mole % of nonpolymeric polybasic acid ion based on the amino group of the chitosan, said membrane being produced by a process comprising the steps of: (I) dissolving chitosan in a dilute aqueous solution of a monobasic acid, (II) producing a membrane composed of a chitosan salt containing a monobasic acid ion, (III) neutralizing the membrane with an aqueous alkaline solution, and (IV) contacting the chitosan membrane thus produced with an acid solution containing at least a nonpolymeric polybasic acid. 
     
     
       5. The membrane for pervaporation of claim 4 in which the polybasic acid is sulfuric acid. 
     
     
       6. The membrane for pervaporation of claim 4 in which the polybasic acid is phosphoric acid.